This invention pertains to the formation of urethane-modified isocyanurate foams using mixtures of polyalkoxylated amines and polyalkoxylated quaternary ammonium borate esters as copolyols. More particularly this invention relates to the use of such copolyols to form foams having NCO/OH ratios of 1.5 to 3.5, using very inexpensive, commercially available resin polyols. A blend of these polyalkoxylated amines and polyalkoxylated quaternary ammonium borate esters with the aforesaid resin polyol and, optionally, a polyether or polyester polyol is very stable and will remain a homogeneous liquid without phase separation and without the need for agitation for at least 7 days after blending.
Urethane and polyisocyanurate foams are manufactured using a blend of an isocyanate and a polyol. The molar ratio of isocyanate to polyol, that is, the ratio of NCO functional groups to OH functional groups, is known as the "index" or "NCO/OH ratio". Foams are manufactured with both isocyanates and polyols and when the molar ratio of isocyanate to polyol is between 1.05 to 1.15, a urethane foam is formed according to the reaction: ##STR1## The urethane product shown above is the monomeric structural unit that combines to form the polyurethane foam. At an index between 1.5 and 3.5, a urethane-modified isocyanurate foam is formed. At indices above 4.1, a isocyanurate foam is formed having the monomeric unit: ##STR2## which may have a minority of urethane linkages. Herein, the terms isocyanurate and polyisocyanurate and the terms urethane and polyurethane in reference to foams will be used interchangably.
Currently, urethane-modified polyisocyanurate foams are manufactured using polyether or polyester polyols, as for example the Voranol.RTM. group of polyols available from Dow Chemical Company, Midland, Mich. When combined with a catalyst, a surfactant, and a blowing agent, and then with an isocyanate in the known manner, these polyether or polyester polyols form a foam having good qualities. Certain resin polyols, such as the Terate.RTM. resin polyol available from Hercules, Incorporated, Wilmington, Del. are of a hydroxyl number sufficient so as to theoretically permit their use in foam manufacture. In practice, however, these polyols have proved to be unacceptable at concentrations in excess of 40% (wt.) of the total polyol blend for use in manufacturing high quality urethane-modified polyisocyanurate foams. Because the resin polyols are about one-third less costly than the currently used conventional polyether or polyester polyols, it is desirable that a polyol blend be found that may be used with larger quantities of such resin polyols to result in a polyisocyanurate foam having acceptable properties and at a lower cost.